2.1 Exercise-Induced Muscle Trauma
Many sports put the participants at risk of direct trauma to muscle, tendon, ligament and subcutaneous tissues, e.g., by contact with the ground, the opponent, a ball or a bat. Much of the pain and disability resulting from soft-tissue trauma is due not to the injury itself but to bleeding in and around the damaged tissue. Extravasated blood causes pain by limiting movement and by local inflammation caused by pro-inflammatory mediators.
Magnesium homeostasis is essential to good health and proper neuromuscular function and magnesium deficiency may result in neuromuscular problems such as muscle cramps, stiffness, pain and spasms. For most athletes performing strenuous exercise, magnesium may be lost from the body. Sweating appears to account for some of this loss. McDonald, R., et. al., 1988, Sports Med., 5: 171-184. However, most magnesium is lost via urinary excretion after exercise, which may be due to metabolic acidosis and increases in aldosterone and antidiuretic hormone. Rayssiguier, Y. et. al., 1990, Magnesium Res., 3: 93-102.
2.2 Neuromuscular Effects
The neuromuscular effects of hypomagnesemia occur commonly in association with hypocalcemia and/or hypokalemia-although the symptoms and signs may be seen in the absence of any other electrolyte abnormalities. Hypomagnesemia associated neuromuscular abnormalities include Trousseau's or Chvostek's signs, tetany, muscle fasciculation, tremor, muscle spasticity, deep tendon reflexes, anxiety, delirium, grand mal seizures, nystagmus, ataxia, vertigo, choreoathetoid movements and dysphagia. Almost all conditions resolve quickly with magnesium replacement. Ntoso, K. A and Goldfarb, S., in Internal Medicine ed. J. H. Stein, 2345-2349, Little, Brown and Company, Inc., (1990). In adolescence, magnesium deficiency may also be associated with muscle pain, early fatigue and stiffness, growing pains and/or Osgood-Schlatter's disease or cramps on strenuous exertion in patients having muscle glycogeneses, Chen, Y-T, in Internal Medicine, ed. W. N. Kelley, 2270-2273 J. B. Lippincott (1992).
2.3 Magnesium
Magnesium is an important element for health and disease. It is the fourth most abundant cation in the human body and is the second most abundant intracellular cation. Elin, R. J., 1987, Clin. Chem., 33: 1965-1970. Magnesium is a cofactor for approximately 300 enzymes and is essential for energy metabolism and for protein and nucleic acid synthesis. Magnesium deficiency may result from a number of factors including decreased intake or increased gastrointestinal or renal loss of magnesium, drug therapy, and alterations in magnesium distribution. Hypomagnesemia is generally defined as a serum magnesium concentration of less than 1.5 mEq/l. The signs and symptoms of hypomagnesemia include arrhythmias, electrocardiographic changes, hypertension, depression, delirium, agitation, tetany, leg cramps, tremors, ataxia, weakness, confusion and convulsions. The ideal intake of magnesium for an adult is 15 to 20 mM/d (350 to 450 mg/d). Magnesium is absorbed primarily in the jejunum and ileum, and healthy persons absorb about 30 to 40 percent of ingested magnesium. The majority of adults have a dietary intake of magnesium less than the recommended dietary allowance (RDA) in the range of 43 to 93.0 percent of RDA. Pao, E. M., Micke, S. J., 1981, Food Technol., 35: 58-69.
Magnesium functions in a wide range of biochemical and physiological processes. Inside cells, magnesium serves as a modulator of many rate limiting enzymes. Extracellular levels of magnesium play an important role in muscle and nerve excitability by maintaining electrical potentials at the membrane. National Research Council, Recommended Dietary Allowances, 10th ed. Washington, D.C.: National Academy Press, 1989, pp. 1, 10-23, 174-205.